Embodiments of the present invention relate to a target for a sputtering chamber.
In the manufacture of integrated circuits and displays, a substrate such as a semiconductor wafer or display panel, is placed in a process chamber and processing conditions are set in the chamber to deposit material on the substrate or to etch the substrate. A typical chamber comprises an enclosure wall that encloses a plasma zone, a substrate support to support the substrate, a gas supply to provide a process gas in the chamber, a gas energizer to energize gas to process the substrate, and a gas exhaust to maintain a gas pressure. Such chambers can include, for example, sputtering (PVD), chemical vapor deposition (CVD), and etching chambers. In a sputtering chamber, a target is sputtered causing sputtered target material to deposit on a substrate facing the target. In the sputtering process, a process gas comprising inert and/or reactive gas is supplied into the chamber, and the target and substrate are electrically biased relative to one another to form energetic ions which bombard the target causing sputtering material to be knocked off the target and deposited as a film on the substrate. In a magnetron sputtering chamber, a magnetic field generator shapes a magnetic field about the target to improve sputtering of the target.
In these sputtering processes, certain regions of the target are often sputtered at higher sputtering rates than other regions, resulting in uneven sputtering of the target surface. For example, uneven target sputtering can arise from the contoured magnetic field used to confine or stir energized gas ions about the target surface. The contoured magnetic field causes target material to be sputtered off at higher rates at particular regions of the target, which can result in the formation of sputtered grooves in the target after its operation for a number of process cycles. The formation of such grooves in the target is undesirable because they subsequently cause uneven deposition of sputtered material across the substrate. Another problem arises when the sputtering plate of the target debonds from the backing plate due to thermal expansion stresses. The cause of these stresses and debonding was not precisely known.
In sputtering processes, it is undesirable to have material sputtered from the target to accumulate on internal surfaces of the chamber, such as chamber wall and component surfaces, as the accumulated deposits can flake off and contaminate the substrate or cause electrical shorts between the chamber walls and target. Thus, the sputtering chamber also includes a process kit which has components that are arranged about the substrate support and chamber sidewalls to receive the sputtering deposits from the target so that these deposits do not accumulate on the chamber walls and other component surfaces. Periodically, the process kit components are dismantled and removed from the chamber for cleaning. However, the sputtered deposits that accumulate on the process kit components can also flake off between cleaning cycles from the thermal stresses generated in the process cycles. The flaked off deposits in the chamber can contaminate the substrate and so are undesirable. While the chamber can be shutdown for cleaning of kit components at shorter time intervals to solve this problem, the resultant chamber downtime further increases processing costs. Thus, it is desirable to have process kit components which are designed to receive and tolerate ever larger amounts of accumulated deposits without sticking to each other or to the substrate, or resulting in flaking off of accumulated deposits during processing. It would also be desirable if the target were shaped to reduce the formation of sputtering deposits on process kit components.